Updated the Jenkins workflow to install in separate directories.

[lsawade]

Description

There seems to be a bug that is triggered at installation of the executables. The only explanation I have is that all pipeline installations happen in the same directory.

This PR fixes that by setting specific CMAKE_INSTALL_PREFIX and removing it afterwards as part of the clean post build.

Alternative is not installing at all, but the process should at least be tested.

Issue Number

-/-

Checklist

Please make sure to check developer documentation on specfem docs.

• I ran the code through pre-commit to check style
• THE DOCUMENTATION BUILDS WITHOUT WARNINGS/ERRORS
• I have added labels to the PR (see right hand side of the PR page)
• My code passes all the integration tests
• I have added sufficient unittests to test my changes
• I have added/updated documentation for the changes I am proposing
• I have updated CMakeLists to ensure my code builds
• My code builds across all platforms